The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Global image archive (6 members)
- Graphic templates (2 members)
- Graphics templates (1 member)
- Great Lakes (1 member)
- Guam (1 member)
- Guideline properties (16 members)
- Hatnote templates (5 members)
- Hatnote templates documentation (1 member)
- Hawaii (1 member)
- Hidden categories (3 members)
- Hidden tags (25 members)
- IPhone (1 member)
- IPhone Instructions (0 members)
- ISO date templates (1 member)
- Icons (14 members)
- Idaho (1 member)
- Illinois (3 members)
- Image required (9 members)
- Image templates (1 member)
- Images (2 members)
- Improper wiki style (0 members)
- Incomplete templates (19 members)
- Index (23 members)
- Indexed pages (2 members)
- Indiana (2 members)
- Indonesia (0 members)
- Info required (7 members)
- Infobox templates (3 members)
- Inline cleanup templates (1 member)
- Inline templates (5 members)
- Interface templates and forms (3 members)
- Internal link maintenance templates (2 members)
- Internal link templates (10 members)
- Iowa (1 member)
- JP (6 members)
- Junction (13 members)
- Kansas (1 member)
- Kentucky (1 member)
- Lang templates (0 members)
- Language Templates (0 members)
- Language templates (1 member)
- Line-handling templates (0 members)
- Linking templates (5 members)
- Live Map (1 member)
- Lock (2 members)
- Locking standards (2 members)
- Louisiana (1 member)
- Maine (3 members)
- Maintenance navigation (1 member)
- Maintenance templates (11 members)